The high-accuracy spectroscopy of H₂ rovibrational transitions in the (2-0) band near 1.2 μm

Abstract

Metrological measurements of rovibrational frequencies in molecular hydrogen provide stringent tests for the most advanced theoretical calculations and for searching for physics beyond the standard model. Here, we report the...

Accurate absolute frequency measurement of the S(2) transition in the fundamental band of H2 near 2.03 μm

“…The limited impact of the choice of the profile on ν 0 has already been discussed in the study of the (2–0) transitions in ref. 5. In addition, we see in Table 2 (as in ref.…”

“…7–11 Very recently, Cozijn and co-workers achieved a feat in saturating the S(0) transition in the 2–0 band of H 2 using the NICE-OHMS technique and a H 2 gas sample at 72 K 12 and reported a transition frequency uncertainty of 8 kHz, in agreement with the frequency measured with a 60 kHz uncertainty in the Doppler regime by comb-referenced cavity ring down spectroscopy (CR-CRDS). 5 This latter work, also including the frequency determination of five other transitions in the 2–0 band, evidenced a systematic underestimation of about 2.58 MHz of the most recent calculated H 2 frequencies, about twice their claimed uncertainties. Apart from these six transition frequencies measured with a sub-MHz uncertainty in the 2–0 band, only the Q(1) transition in the 1–0 band has been measured with such a level of accuracy.…”

“…22 and confirms the fact that ab initio values are systematically smaller than experimental ones for H 2 and its isotopologues. 5,6,11 This tendency is illustrated in Fig. 3 which compares the H 2 transition frequencies of the 1–0 and 2–0 bands referenced to an absolute frequency standard to the best ab initio values.…”

“…In addition, we see in Table 2 (as in ref. 5) that the δ 2 value has a very limited impact on the retrieved ν 0 value.…”

“…Up to now, such measurements were relatively scarce (ref. 5, 6 and references herein). Most of them were obtained by Doppler limited spectroscopy.…”